**Core Concept**
The question is testing the student's knowledge of a specific type of poisoning that affects the process of putrefaction. Putrefaction is the breakdown of tissue by microorganisms, typically bacteria, after death. The correct answer is a substance that inhibits the growth of these microorganisms or slows down the putrefaction process.

**Why the Correct Answer is Right**
The correct answer is **Antimony**. Antimony, specifically antimony potassium tartrate, is a substance that has been known to retard putrefaction. This is because antimony has antimicrobial properties, which inhibit the growth of bacteria and other microorganisms that break down tissue. The mechanism of action involves the inhibition of microbial enzymes, ultimately leading to a slower rate of putrefaction.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not specified, so we will move on to the next one.
**Option B:** Mercury poisoning is known to cause a range of systemic effects, but it does not specifically retard putrefaction.
**Option C:** Lead poisoning is a serious condition, but it does not have a direct effect on the process of putrefaction.
**Option D:** Arsenic poisoning is known to cause a range of systemic effects, including gastrointestinal symptoms, but it does not specifically retard putrefaction.

**Clinical Pearl / High-Yield Fact**
When considering poisoning in a deceased individual, it is essential to be aware of the effects of different substances on the body. Antimony poisoning, in particular, can be challenging to diagnose due to its nonspecific symptoms and the fact that it can be mistaken for other types of poisoning. A high index of suspicion and thorough laboratory testing are necessary to confirm antimony poisoning.

**Correct Answer: B. Mercury poisoning is known to cause a range of systemic effects, but it does not specifically retard putrefaction.